1. Field of the Invention
The invention generally relates to apparatuses and methods for measurement control in a wireless communications system, and more particularly, to apparatuses and methods for managing measurement configurations of component carriers in a wireless communications system.
2. Description of the Related Art
Due to mobile communication technology advancements in recent years, various communication services, such as voice call services, data transfer services, and video call services, etc., may be provided to users regardless of their locations. Most mobile communications systems are multiple access systems in which access and wireless network resources are allocated to multiple users. The multiple access technologies employed by the mobile communications systems include the 1x Code Division Multiple Access 2000 (1x CDMA 2000) technology, the 1x Evolution-Data Optimized (1x EVDO) technology, the Orthogonal Frequency Division Multiplexing (OFDM) technology, and the Long Term Evolution (LTE) technology. Evolved from the LTE, the LTE Advanced is a major enhancement of the LTE standard. The LTE Advanced should be compatible with LTE equipment, and should share frequency bands with the LTE communications system. One of the important LTE Advanced benefits is its ability to take advantage of advanced topology networks, wherein optimized heterogeneous networks have a mix of macros with low power nodes such as picocells, temtocells and new relay nodes.
In addition, the LTE Advanced also introduces a multicarrier feature so as to be able to use ultra wide bandwidth, up to 100 MHz of a spectrum and support very high data rates. The multicarrier feature introduced in the LTE Advanced is supported by Carrier Aggregation (CA). In CA, two or more Component Carriers (CCs) are aggregated in order to provide wider transmission bandwidths up to 100 MHz. The CA can be applied to aggregate both contiguous and non-contiguous CCs. It is also possible to configure a User Equipment (UE) to aggregate a different number of CCs originating from the same evolved Node B (eNB) and of possibly different bandwidths in the uplink (UL) and the downlink (DL). The UE may simultaneously receive or transmit radio frequency (RF) signals via one or multiple CCs depending on its capabilities. A record of configured set of CCs aggregated for signal and data transmission may be maintained by both the UE and the eNB for keeping information regarding to the configured CCs for the UE.
However, the number of CCs in the configured set may be changed due to network conditions. For example, a new CC with good signal quality may be qualif?ied by the eNB and then added into the configured set of CCs. On the contrary, when signal quality of a CC in the configured set becomes poor, the eNB may decide to remove it from the configured set. Generally, each CC corresponds to at least one measurement configuration for configuring the measurement task corresponding to the CC. The measurement tasks corresponding to the CCs are performed by the UE so as to periodically or nonperiodically measure signal quality of the CC, for example by measuring Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ) or Received Signal Strength Indicator (RSSI) of the CC. When content of the configured set of CCs has been changed, how to manage the measurement configuration(s) corresponding to the added or removed CC(s) is a problem which eagerly needs to be solved.